How Often Should I Replace My Air Filter?

If you've ever had your furnace fail in the dead of winter—or your air conditioner kick out on you in the sweltering heat of summer—you know that indoor comfort does not come cheap. The cost to repair or replace an old unit is steep, to be sure, so take the steps now to make sure yours has a long and happy life. First step? Make sure you change the air filter as often as necessary.

But how often is necessary when it comes to replacing your air filter? Well, it depends on a few different things:

Your PetsIf you have pets that shed, their hair or fur can be pulled into your air conditioner and furnace through your duct work. When your unit is working overtime—like, hey... right now when it's super freezing outside—the air filter may need to be changed as often as once a month.

Your (or Your Guests') AllergiesIf you, your family or your weekend couch surfers suffer from dust or mold allergies, a fresh air filter will make everyone more comfortable. If you're very sensitive to dust, change your air filter once a month. Otherwise, a four- to six-times-a-year replacement routine should keep air quality up for everyone.

Your Air Filter...Pro tip: There are a billion different sizes and kinds of air filters on the market (You may have discovered this when you accidentally bought the wrong size filter because you didn't store the measurements in your phone like we suggested). Bigger air filters (both in width and thickness) can stand to be changed less often, while super-compact filters should get more frequent attention.

...And How Often You Clean ItIf you regularly vacuum dust and loose dirt from your air filter, you can double the life of it. A normal person without a shedding pet or severe allergies should change their air filter roughly four times each year, but thorough cleaning can cut that down to just two times.